Pixel circuit driving method, pixel circuit, display panel and display device

Abstract

The invention provides a driving method of a pixel circuit, the pixel circuit, a display panel and a display device.The pixel circuit has a black insertion stage and an initialization stage arranged before the black insertion stage, and the driving method of the pixel circuit comprises the steps that the pixel circuit is conducted in the initialization stage so as to control the pixel circuit to release charges; in other words, before the black insertion stage, the redundant charges in the pixel circuit can be released in the initialization stage, so that the situation that in the black insertion stage and the subsequent display stage, the display of a display screen is poor due to the redundant charges is avoided.

Description

Technical Field

[0001] The present application belongs to the technical field of display devices, and in particular, relates to a driving method of a pixel circuit, a pixel circuit, a display panel, and a display device. Background Art

[0002] Organic Light Emitting Display (OLED) and flat panel display devices based on technologies such as Light Emitting Diode (LED) have the advantages of high image quality, power saving, thin body and wide application range, and are widely used in various consumer electronic products such as mobile phones, televisions, laptops, desktop computers, etc., becoming the mainstream in display devices.

[0003] However, the performance of current OLED display products needs to be improved. Summary of the invention

[0004] The purpose of the present application is to provide a driving method for a pixel circuit, a pixel circuit, a display panel and a display device, aiming to solve the problem of poor display of the display panel in the traditional technology.

[0005] A first aspect of an embodiment of the present application provides a driving method for a pixel circuit, wherein the pixel circuit has a black insertion stage and an initialization stage arranged before the black insertion stage, and the driving method includes:

[0006] The pixel circuit is turned on during the initialization phase to control the pixel circuit to release charges.

[0007] In some embodiments of the present application, turning on the pixel circuit in the initialization stage to control the pixel circuit to release charge includes:

[0008] An initialization signal is obtained, and the pixel circuit is controlled to be turned on according to the initialization signal; wherein the initialization signal includes an enable input signal and an enable clock signal.

[0009] In some embodiments of the present application, before obtaining the initialization signal and controlling the pixel circuit to be turned on according to the initialization signal, the process includes:

[0010] The minimum luminous brightness of the pixel circuit is set to be greater than 0 nit.

[0011] In some embodiments of the present application, the pixel circuit includes a display branch and a compensation branch, the display branch includes a first power line, a light emitting diode, and a second power line connected in sequence, the compensation branch is connected between the first power line and the light emitting diode, a first transistor is provided on the compensation branch, and a drain electrode of the second transistor is connected between the first power line and the light emitting diode; the driving method further includes:

[0012] In the black insertion stage, the first transistor is turned off.

[0013] In some embodiments of the present application, the first transistor is a TFT, a drain electrode of the first transistor is connected between the first power line and the light emitting diode, a source electrode of the first transistor is used to receive a black insertion voltage, and in the black insertion stage, turning off the first transistor includes:

[0014] A black insertion voltage is obtained and the black insertion voltage is set low to turn off the first transistor.

[0015] In some embodiments of the present application, the step of obtaining a black insertion voltage and setting the black insertion voltage low to turn off the first transistor includes:

[0016] The main control chip sets the black insertion voltage to a low level according to the analog power supply voltage on the main control chip.

[0017] In some embodiments of the present application, the main control chip sets the black insertion voltage to a low level according to the analog power supply voltage on the main control chip, including:

[0018] The main control chip sets the black insertion voltage to a low level until the black insertion voltage is lower than the analog power supply voltage.

[0019] In a second aspect, the present application also provides a pixel circuit that is driven using the above-mentioned driving method.

[0020] In a third aspect, the present application also provides a display panel, which includes the above-mentioned pixel circuit.

[0021] In a fourth aspect, the present application also provides a display device, which includes the above-mentioned display panel.

[0022] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned driving method of a pixel circuit, a pixel circuit, a display panel and a display device, the pixel circuit has a black insertion stage and an initialization stage arranged before the black insertion stage, and the driving method of the pixel circuit includes turning on the pixel circuit in the initialization stage to control the pixel circuit to release charge; that is, before the black insertion stage, the excess charge in the pixel circuit can be released in the initialization stage to avoid poor display of the display screen due to the excess charge in the black insertion stage and its subsequent display stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a circuit structure of a pixel circuit provided in an embodiment of the present application;

[0024] Figure 2 A schematic diagram of the steps of a driving method provided in an embodiment of the present application;

[0025] Figure 3 A schematic diagram of the steps of a driving method provided in another embodiment of the present application;

[0026] Figure 4 A schematic diagram of the steps of a driving method provided in another embodiment of the present application;

[0027] Figure 5 A schematic diagram of a circuit structure of a pixel circuit provided in another embodiment of the present application;

[0028] Figure 6 A schematic diagram of the steps of a driving method provided in yet another embodiment of the present application;

[0029] Figure 7 A schematic diagram of the steps of a driving method provided in yet another embodiment of the present application;

[0030] Figure 8 A schematic diagram of the steps of a driving method provided in yet another embodiment of the present application;

[0031] Fig. 9 A signal timing diagram provided for an embodiment of the present application.

[0032] Specific element symbol description: T1-first transistor, T2-second transistor, T3-third transistor, T4-fourth transistor, T5-fifth transistor, T6-sixth transistor, T7-seventh transistor, C2-first capacitor, 100-display branch, 200-compensation branch. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0035] It should be understood that the terms "length", "width", "up", "down", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] It is important to know that with the rapid development of electronic technology, portable devices such as tablets have become an indispensable part of people's daily lives. OLED (organic electroluminescent) screens are widely used in these devices and are popular for their excellent color performance, high contrast and low energy consumption. However, in actual use, OLED screens may face a variety of complex electrical problems, one of which is the residual charge effect caused by electrostatic discharge (ESD) and the resulting screen abnormalities.

[0038] Electrostatic discharge (ESD) is a phenomenon in which an imbalance of charge occurs between two objects or between an object and the ground, resulting in a sudden discharge. This discharge may not only cause transient failures, performance degradation, or even permanent damage to electronic devices and components, but may also cause a series of subsequent problems due to the presence of residual charge. In the production and use of devices such as tablets, the accumulation and discharge of static charges are particularly common. For example, the friction between the human body and the ground while walking and wearing synthetic fiber clothing can lead to static electricity accumulation. When these static charges are not completely dissipated and there are design deficiencies in the internal circuits of the device, a series of electrical failures may occur.

[0039] In the application of OLED screens, the existence of residual charge after electrostatic discharge is a particularly serious problem. When the residual charge is conducted through the OLED lighting path, it may cause abnormal phenomena such as green flashing on the screen in specific areas (such as the R corner position). The root cause of this phenomenon is that static charge affects key components in the OLED circuit, such as the driving thin-film transistor (TFT) and the switching transistor, causing them to turn on incorrectly when they should not be turned on. Traditional methods often focus on preventing the occurrence of electrostatic discharge, such as establishing an electrostatic protection area, using anti-static tools and equipment, etc., but lack targeted countermeasures for electrostatic discharge that has occurred and its subsequent effects.

[0040] Therefore, based on this, the present application improves the driving method of the related pixel circuit, the pixel circuit, the display panel and the display device.

[0041] See also Figure 1 and Figure 2 , Figure 1 FIG. 4 shows a schematic diagram of a circuit structure of a pixel circuit provided in this embodiment. Figure 2 A schematic diagram of the steps of the driving method provided in this embodiment is shown. The pixel circuit in this embodiment is a 7T1C circuit, but the driving method of the present application is not limited to the 7T1C circuit, and can also be applied to other pixel circuits such as 3T1C, 4T1C, 5T1C, 6T1C, etc. In the driving method of the pixel circuit of this embodiment, the pixel circuit has a black insertion stage and an initialization stage arranged before the black insertion stage, and the driving method includes: S200: turning on the pixel circuit in the initialization stage to control the pixel circuit to release charge.

[0042] It needs to be explained that in the initialization stage, the relevant transistors in the pixel circuit are turned on by a control signal (such as an initialization signal or a scan signal). After being turned on, the capacitors and other storage elements in the pixel circuit begin to release the previously stored charges to prepare for the next display cycle. The purpose of releasing the charge is to eliminate the charge or voltage that may remain after ESD or in the previous display cycle to avoid affecting the current display cycle. The black insertion stage is usually located between two display frames and is used to insert a short dark period between display frames. This helps to reduce the afterimage phenomenon of the display panel and improve the clarity and smoothness of dynamic images.

[0043] In the current pixel circuit driving method, the excess charge is not removed in advance, resulting in a green flash phenomenon on the display panel after the display panel is turned on. However, the present application can release the excess charge in the pixel circuit in the initialization stage before the black insertion stage to avoid poor display of the display screen due to the excess charge in the black insertion stage and the subsequent display stage.

[0044] It is understandable that the R corner of the display panel is more prone to green flash. On the one hand, the edge area of ​​the screen, including the R corner, may have differences in electrical properties due to the particularity of its geometry and position. For example, the electric field distribution, current density, etc. in the edge area may be different from those in the central area, which may lead to differences in the distribution and dissipation process of residual charge after ESD. On the other hand, the circuit paths at the edge of the screen may have different resistance and capacitance values, and these differences will affect the flow and dissipation speed of the charge. At the curvature change such as the R corner, the accumulation and dissipation of charge may be more complicated, thereby increasing the risk of green flash.

[0045] In some embodiments of this application, please refer to Figure 3 , Figure 3 A schematic diagram of the steps of the driving method provided in this embodiment is shown; step S200 of this embodiment includes: S210: obtaining an initialization signal, and controlling the pixel circuit to be turned on according to the initialization signal; wherein the initialization signal includes an enable input signal and an enable clock signal.

[0046] Specifically, the enable input signal (Enable input, EIN) is used to control the activation state of the pixel circuit, that is, as a light-emitting control signal of the pixel circuit. Exemplarily, if the enable input signal is set low, the pixel circuit enters the working state, and if the enable input signal is set high, the pixel circuit enters the dormant or closed state. The enable clock signal (Enable Clock, ECLK) is used to synchronize data transmission, status update or other operations that require precise timing control in the pixel circuit, which can ensure that the relevant clock signal is stable before the OLED pixel starts to receive data, thereby avoiding data transmission problems or display anomalies caused by timing errors. Exemplarily, the enable clock signal can be used as a scanning signal for the pixel circuit.

[0047] It can be understood that by moving the enable input signal and the enable clock signal forward to start toggle (state switching) before the black insertion stage; when the whole machine wakes up the screen, the enable input signal is advanced, which can effectively make the display panel discharge in an effective path, and there will be no abnormal green flashing after the charge is released.

[0048] In some embodiments, during the initialization process, the conduction state of the pixel circuit is achieved by controlling transistors (such as TFTs, thin film transistors) in the circuit. These transistors act as switches to allow or prevent the flow of current depending on the state of the input signal (high level or low level).

[0049] In some embodiments of this application, please refer to Figure 4 , Figure 4A schematic diagram of the steps of the driving method provided by this embodiment is shown; before step S200, this embodiment includes: S100: setting the minimum luminous brightness of the pixel circuit to be greater than 0 nit.

[0050] It should be explained that in the related art, the DBV value (i.e., the brightness) will not be set first when the whole machine is powered on. The default setting of DBV value is 0 (at this time, the enable input signal is in a high level state because the duty cycle is 0), and the brightness value will be cut after the picture is cut. Only when a certain DBV value is cut will the EIN switching state be set, and then it can be displayed normally. In this embodiment, the minimum luminous brightness is set to be greater than 0 nits, so that the power-on enable input signal will have a switching state setting, and the enable input signal starts to switch state before the Source. At this time, the thin film transistor is continuously discharged through the residual charge to avoid flickering when the discharge starts when the Source starts to start.

[0051] In some embodiments, the minimum luminance of the pixel circuit is 2 nits. That is, the DBV value is 8 and the duty cycle is not 0.

[0052] In some embodiments of this application, please refer to Figure 5 as well as Figure 6 , Figure 5 FIG. 4 shows a schematic diagram of a circuit structure of a pixel circuit provided in this embodiment. Figure 6 The schematic diagram of the steps of the driving method provided by the present embodiment is shown. The pixel circuit of the present embodiment includes a display branch 100 and a compensation branch 200, the display branch 100 includes a first power line, a light emitting diode and a second power line connected in sequence, the compensation branch 200 is connected between the first power line and the light emitting diode, and a first transistor T1 is arranged on the compensation branch 200, and the drain electrode of the first transistor T1 is connected between the first power line and the light emitting diode. The driving method of the present embodiment also includes: S300: in the black insertion stage, turning off the first transistor T1.

[0053] It can be understood that after the first transistor T1 is turned off, the leakage current cannot flow through the first transistor T1, which is beneficial to reducing leakage current and weakening the screen flicker phenomenon.

[0054] In some embodiments, the first power line is a positive power line, and the second power line is a negative power line.

[0055] In some embodiments of this application, please continue to refer to Figure 5 Also see Figure 7 , Figure 7A schematic diagram of the steps of the driving method provided in this embodiment is shown, the first transistor T1 is a TFT transistor, the drain electrode of the first transistor T1 is connected between the first power line and the light-emitting diode, and the source electrode of the first transistor T1 is used to receive the black insertion voltage. Step S300 includes: S310: obtaining the black insertion voltage and setting the black insertion voltage low to turn off the first transistor T1.

[0056] Specifically, first obtain the current black insertion voltage value. The black insertion voltage is an adjustable voltage value used to achieve specific display effects during the display process, such as reducing afterimages, improving contrast, etc. The black insertion voltage is then adjusted to a lower value so that Vgs (the voltage difference from the gate electrode to the source electrode) no longer meets the conditions for the TFT transistor to be turned on (i.e., Vgs>=Vth, but this is a reverse operation, because reducing the black insertion voltage actually increases the absolute value of Vgs, but due to the characteristics of the PMOS tube, increasing the absolute value of Vgs will cause it to be turned off). Therefore, by reducing the black insertion voltage, it can be ensured that the first transistor T1 is turned off, thereby cutting off the current path from the first power line to the light-emitting diode.

[0057] In some embodiments of this application, please refer to Figure 8 , Figure 8 A schematic diagram of the steps of the driving method provided by this embodiment is shown; step S310 includes: S311: the main control chip sets the black insertion voltage to a low level according to the analog power supply voltage on the main control chip.

[0058] It needs to be explained that in the display panel, the main control chip is the core component responsible for controlling and managing the entire display process. It receives signals from the outside (such as user input, video signals, etc.) and generates corresponding control signals to control various components on the display panel (such as TFT transistors, OLED light-emitting diodes, etc.). There are usually multiple power supplies on the main control chip, including analog power supply voltage. This power supply is used to provide a stable voltage for the analog circuit part on the chip to ensure the accuracy and stability of analog signal processing. The value of the analog power supply voltage is fixed or can be adjusted within a certain range, but it is not directly equal to the black insertion voltage. The main control chip will use the analog power supply voltage as a reference or benchmark based on its internal logic and algorithm, as well as the current display requirements, to generate and output a lower black insertion voltage value. This black insertion voltage value is then applied to the source electrode of the first transistor T1 to change the voltage difference (Vgs) from its gate electrode to the source electrode, thereby controlling the on or off state of the transistor.

[0059] In some embodiments of the present application, step S311 includes: the main control chip sets the black insertion voltage to a low level until the black insertion voltage is lower than the analog power supply voltage.

[0060] In some embodiments, the black insertion voltage is 5V - 7V. Specifically, the black insertion voltage is 6V.

[0061] It should be noted that, on the one hand, the turn-on state condition of the first transistor T1 is Vgs < Vth. Reducing the black insertion voltage, that is, reducing the source electrode voltage of the first transistor T1, increases Vgs (Vgs = Vg - Vs), turns off the first transistor T1, and reduces leakage current.

[0062] On the other hand, since SIN is turned on in advance during this process, the compensation signal will exist at the source electrode of the second transistor T2. When the next stage starts (after the first power supply line starts to conduct), the light-emitting path conducts. At this time, the accumulated high voltage will be released first, resulting in a flicker phenomenon. Therefore, the first transistor T1 can be turned off to reduce the flicker phenomenon.

[0063] Please continue to refer to Figure 5 and refer to Fig. 9 , Fig. 9 shows the signal timing diagram provided in this embodiment. ELVDD is the positive power supply line, ELVSS is the negative power supply line, EIN is the enable input signal (light-emitting control signal), SOURCE is the black insertion signal, and ECK is the enable clock signal (scanning signal). This embodiment includes a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, a seventh transistor T7, a first capacitor C1, and a light-emitting diode.

[0064] The fifth transistor T5, the second transistor T2, the sixth transistor T6, and the light-emitting diode are connected in series between the positive power supply line and the negative power supply line to form a display branch. One end of the first transistor T1 is connected between the second transistor T2 and the fifth transistor T5, and the other end is connected to the Data signal to form a compensation branch. One end of the seventh transistor T7 is disposed between the sixth transistor T6 and the light-emitting diode, and the other end is connected to the second reference voltage; the control electrode of the seventh transistor T7 is connected to the S3 signal. One end of the first capacitor C1 is connected between the fifth transistor T5 and the positive power supply line, and the other end is connected to the fourth transistor T4. The other end of the fourth transistor T4 is connected to the first reference voltage, and the control electrode of the fourth transistor T4 is connected to the S1 signal. One end of the third transistor T3 is connected between the second transistor T2 and the sixth transistor T6, and the other end is connected between the first capacitor C1 and the fourth transistor T4. The control electrodes of the third transistor T3 and the first transistor T1 are commonly connected to the S2 signal. The control electrode of the second transistor T2 is connected between the first capacitor C1 and the fourth transistor T4. The control electrodes of the fifth transistor T5 and the sixth transistor T6 are commonly connected to the EM signal.

[0065] Specifically, after an ESD event, if the EM signal is in the on state due to residual charge, and the switching transistors such as the first transistor T1 and the sixth transistor T6 cannot be turned off normally due to the positive drift of the threshold voltage (Vth), the source supply current may flow into the OLED through an unexpected path, causing the screen to flash green. This phenomenon is particularly obvious under the monitoring of an oscilloscope and a photoelectric probe. The flashing position is highly consistent with the power-on position of the source signal, further confirming the interference of the electrostatic residual charge on the circuit state.

[0066] In some embodiments, the third transistor T3 includes a first sub-transistor and a second sub-transistor connected in series. The fourth transistor T4 includes a third sub-transistor and a fourth sub-transistor connected in series.

[0067] In some embodiments, the first transistor T1 , the second transistor T2 , the third transistor T3 , the fourth transistor T4 , the fifth transistor T5 , the sixth transistor T6 , and the seventh transistor T7 are all TFT transistors.

[0068] Furthermore, in order to better implement the driving method of the pixel circuit in any of the above embodiments, based on the above driving method of the pixel circuit, the present application also provides a pixel circuit that is driven by the above driving method.

[0069] Furthermore, in order to better implement the pixel circuit in any of the above embodiments, the present application also provides a display panel, which includes the above pixel circuit.

[0070] In some embodiments, the display panel may be an OLED display panel.

[0071] Furthermore, in order to better implement the display panel in any of the above embodiments, the present application also provides a display device, which includes the above display panel.

[0072] In some embodiments, the display device may be a mobile phone, a tablet, a computer, etc.

[0073] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0074] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0075] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0076] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0077] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for driving a pixel circuit, characterized in that: The pixel circuit has a black insertion phase and an initialization phase arranged before the black insertion phase, and the driving method includes: The pixel circuit is turned on during the initialization phase to control the pixel circuit to release charges.

2. The driving method according to claim 1, characterized in that: The step of turning on the pixel circuit in the initialization stage to control the pixel circuit to release charge comprises: An initialization signal is obtained, and the pixel circuit is controlled to be turned on according to the initialization signal; wherein the initialization signal includes an enable input signal and an enable clock signal.

3. The driving method according to claim 2, characterized in that: Before obtaining the initialization signal and controlling the pixel circuit to be turned on according to the initialization signal, the method includes: The minimum luminous brightness of the pixel circuit is set to be greater than 0 nit.

4. The driving method according to any one of claims 1 to 3, characterized in that: The pixel circuit comprises a display branch and a compensation branch, the display branch comprises a first power line, a light emitting diode and a second power line connected in sequence, the compensation branch is connected between the first power line and the light emitting diode, a first transistor is arranged on the compensation branch, and a drain electrode of the first transistor is connected between the first power line and the light emitting diode; The driving method further comprises: In the black insertion stage, the first transistor is turned off.

5. The driving method according to claim 4, characterized in that: The first transistor is a TFT, a source electrode of the first transistor is used to receive a black insertion voltage, and in the black insertion stage, turning off the first transistor includes: A black insertion voltage is obtained and the black insertion voltage is set low to turn off the first transistor.

6. The driving method according to claim 5, characterized in that: The step of obtaining a black insertion voltage and setting the black insertion voltage low to turn off the first transistor comprises: The main control chip sets the black insertion voltage to a low level according to the analog power supply voltage on the main control chip.

7. The driving method according to claim 6, characterized in that: The main control chip setting the black insertion voltage low according to the analog power supply voltage on the main control chip includes: The main control chip sets the black insertion voltage to a low level until the black insertion voltage is lower than the analog power supply voltage.

8. A pixel circuit, characterized in that: The driving method according to any one of claims 1 to 7 is used for driving.

9. A display panel, characterized in that: The display panel comprises the pixel circuit according to claim 8.

10. A display device, characterized in that: The display device comprises the display panel according to claim 9.

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